Date of Award
Master of Science
Plant and Soil Science
Food products are susceptible to contamination by food spoilage and pathogenic bacteria during their production, processing, packaging, storage, transportation and distribution. Thus, to improve food quality and safety, various chemical, natural preservative and antimicrobial food coating / packaging are used. Because of health concerns there is increasing trend towards the use of natural antimicrobials such as plant extract and essential oils for preservation of food as well as for application into the antimicrobial food coating and packaging. Different techniques are being used to improve their antimicrobial activity. Encapsulation of antimicrobial into liposome is one of them. The main objective of this study was to evaluate the antimicrobial activity of selected plant based antimicrobial compounds before and after their encapsulation into the 10,12- Pentacosadiynoic Acid (PDA, commonly known as Polydiacetylene acid) lipsome and immobilization on common food contact surfaces (glass and poly lactic acid film). Antibacterial activities of Curcumin, Resveratrol, Cinnamaldehyde, p-Coumaric acid and Coniferyl alcohol were studied at four different concentration (60, 120, 180 and 240 μg/ml) against E. coli W1485 and vegetative cells of B. cereus by shake flask assay in phosphate buffer saline (PBS) at pH 7.0. Curcumin, Resveratrol, Cinnamaldehyde, p-Coumaric acid and Coniferyl alcohol reduced E. coli W1485 cells to 2.84, 5.95, 3.56, 2.04 and 3.06 log10 CFU/ml respectively within 48 h at 240 μg/ml. Curcumin, p-Coumaric acid and Coniferyl alcohol reduced B. cereus cells to 4.32, 1.95 and 2.8 log10 CFU/ml respectively within 48 h at 240 μg/ml. Resveratrol and Cinnamaldehyde reduced B. cereus cells to an undetectable level within 32 and 4 h respectively at 240 μg/ml. Liposomal encapsulated Curcumin and Cinnamaldehyde reduce E. coli W1485 and B. cereus cells to an undetectable level within 8 h of incubation at 560 and 864 ng/ml of concentration respectively. The results demonstrated that antimicrobial activity increased after encapsulation into the PDA liposome. Encapsulated Curcumin immobilized on glass slides showed 2.19 log10 CFU/ml reduction of E. coli W1485 and 0.76 log10 CFU/ml reduction of vegetative cells of B. cereus. Encapsulated Cinnamaldehyde immobilized on glass slide showed 2.56 log10 CFU/ml reduction of E. coli W1485 and 1.59 log10sub CFU/ml reduction of vegetative cells of B. cereus. PLA film containing Cinnamaldehyde showed 50% inhibition of E. coli W1485 and B. cereus in milk within 48 h of incubation, but after that it did not show any antibacterial activity. Plant based natural antimicrobials have potential application in food safety and their antibacterial activity can be further improved by liposomal encapsulation.
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